Domestic robots such as nursing care robots and housekeeping support robots have been developed actively in recent years. Industrial robots including a robot cooperating with a person have been also developed actively due to increasing cell production plants and the like. Such an assisting robot cooperating with a person needs to coexist with a person, unlike a conventional robot configured to move in a robot operating area separated from a person staying area. The assisting robot is required to assure safety different from that required for the conventional industrial robots and the like. A power assisting robot for performing a task of conveying an object in cooperation with a person is in one of a state of conveying an object and a state of conveying no object, and needs to be safely switched between these two states. The robot needs to contact to hold an object when being switched from the state of conveying no object to the state of conveying an object. When the power assisting robot is made in contact with an object, a force detector detects force in a direction unintended by a person due to the contact. Upon the detection of force in a direction unintended by a person, the robot may move in an unintended direction or may be hard to be pressed against the object. The conventional assisting robots have such safety problems.
A conventional technique for such a power assisting robot configured to hold an object provides a method of controlling a held object (work) so as to move as desired by directionally limiting motion of an assisting device in accordance with a direction of operation force (Patent Literature 1).